Which factions (emphasis on the plural!) do you actually play on a regular basis?

[gollum]

Regulars
Byzantines;
interesting position (crossroads or north/south, east/west) with rich lands and good trade potential, interesting adaptable roster (overpowered for early, obsolete for late) that can play missile heavy or melee heavy, infantry heavy or cavalry heavy, focusing on speed armor or firepower depending on the circumstances, would be much better to have less byzantine infantries at the start, a fort in constantinople and no +2 influence for the faction leader that is responsible for the jedi kataphraktoi princes. Try to limit yourself in building Varangians; way overpowered.
Almohads;
interesting roster based on effective militias and desert specialist units but lacking in heavy cavalry (gulams only). Nice GA goals; AUM overpowered for early and too cheap - provides a way to play with more melee heavy tactics which is a good tactical addition for a muslim faction. As with the other Islamic factions makes for a fun campaign as the catholic world targets you with crusades and outright aggression.
Egyptians;
Nice roster with solid infantry and missiles (saracens, deserrt archers, nizaris), desert specialists and good cavalry choices (Kwarazmians, Mamelukes), no uber units - top notch in desert environments, ok in arid, terrible in lush and temperate. Very rich lands with very good trade potential; fun GA goals (the Jihad for Asia).
Turks;
Interesting continuously evolving roster; excellent hybrids (melee/missile), excellent cavalry of all types + eventually the excellent Janissaries, challenging initial position for new players (requires immediate action) and vulnerable to the Mongol Invasion make up for a busy campiagn until the mid-high era; after that you can decide where to go.
HRE;
typical melee/armor heavy catholic roster+the excellent mounted crossbows. Access to the Gothic line of troops that is worth the wait. Containing Swizzerland and Tyrolia that can provide a considerable advantage with their pikes and Halberds eventually. Slow start and problems with weak central position, poor lands and the papacy. Makes for a turtle struggling game until you have conquered at least half of your neighbours (say the Italians Poles and Huns); interesting GA goals.
French;
challenging position and generic catholic roster; the best GA goals of the game.
Sicilians;
interesting initial position that makes for high replayability as campaigns may develop in a huge variety of ways due to the many options available (can go after... anyone really). faces the player with the stretgic choice of when to stop picking opportunistically opponents and try to supplant them. Generic catholic roster.
Russians;
interesting and challenging position especially in early; a challenge throughout early and high as you take over the steppes, build them up slowly and by the time you are ready to take on someone the Horde appears. Nice roster with reliable swift horses (boyars, steppe cavalry, horse archers) and catholic style mediocre militia infantry and solid spearmen (armoured spearmen, rus spearmen). resrtain your self from the cheat of using dismounted druzhinas.

Occasionals
Aragonese; the Spanish with a more challenging position. The game can also develop in different ways ie focus in Iberia, focus on France or take it to the seas. Access to Lancers that are worth the wait.

Can't stand
The English; way too safe position and overpowered special units on top of the overpowered Catholic roster
The Spanish; too much money in Iberia and starting with 2 provinces in a semi-safe position close to bottlenecks makes them very boring. Once you reach Morocco and navarre/Aragon its effectively game over and this can be achieved in 10 turns.
The Italians; too easy to Blitz the French and Germans from a safe, rich position. Within 10-20 turns you have supplanted them both and the game starts feeling boring
The Danes; already overowered before VI due to the Vikings units and their availability (Fort), with VI the Danes became even more so due to the landsmen and huscarles. Vikings should have homelands in Scandinavia and Russia. As it stands the danish game is uninteresting in terms of replay, as once the blitz starts it just goes on and on.

Indifferent
The Hungarians; just never gave them a serious go
The Poles; just never gave them a serious go, although Caravel's description (in the favorite 2009 faction thread) convinced me to do so at some point.